I had a very bad experience with an Audiogon seller a few years back. I purchased an Audio Research CA50 integrated amp. Unfortunately for me, if they had only auditioned it properly over a week before putting it up for sale, they would have noticed a very loud random popping noise. I did a little research and found out it may have been a defective power supply issue overheating the tubes. In fact, one of the tubes had overheated so badly that it melted the hard rubber tube ring around it! I’m not going to name the dealer, but I’ll never buy anything from them again, even though their Audiogon feedback is stellar. I could not convince him to take it back. I subsequently sold it at a loss. It was just my bad luck, I guess. BTW, when I sold it I FULLY DISCLOSED all of the the issues with the unit. That is all any of us want when we buy used gear.